/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.hadoop.hbase.regionserver;

import java.security.PrivilegedAction;

import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.RegionInfo;
import org.apache.hadoop.hbase.client.RegionInfoBuilder;
import org.apache.hadoop.hbase.regionserver.RegionServerServices.RegionStateTransitionContext;
import org.apache.hadoop.hbase.security.User;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.yetus.audience.InterfaceAudience;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.hbase.thirdparty.com.google.common.base.Preconditions;

import org.apache.hadoop.hbase.shaded.protobuf.generated.RegionServerStatusProtos.RegionStateTransition.TransitionCode;

/**
 * Handles processing region splits. Put in a queue, owned by HRegionServer.
 */
@InterfaceAudience.Private
class SplitRequest implements Runnable {
    private static final Logger LOG = LoggerFactory.getLogger(SplitRequest.class);
    private final RegionInfo parent;
    private final byte[] midKey;
    private final HRegionServer server;
    private final User user;

    SplitRequest(Region region, byte[] midKey, HRegionServer hrs, User user) {
        Preconditions.checkNotNull(hrs);
        this.parent = region.getRegionInfo();
        this.midKey = midKey;
        this.server = hrs;
        this.user = user;
    }

    @Override
    public String toString() {
        return "regionName=" + parent + ", midKey=" + Bytes.toStringBinary(midKey);
    }

    private void doSplitting() {
        server.metricsRegionServer.incrSplitRequest();
        if(user != null && user.getUGI() != null) {
            user.getUGI().doAs(new PrivilegedAction<Void>() {
                @Override
                public Void run() {
                    requestRegionSplit();
                    return null;
                }
            });
        } else {

            /********
             * TODO_MA 马中华 https://blog.csdn.net/zhongqi2513
             *   注释：
             */
            requestRegionSplit();
        }
    }


    /********
     * TODO_MA 马中华 https://blog.csdn.net/zhongqi2513
     *   注释：
     */
    private void requestRegionSplit() {
        final TableName table = parent.getTable();

        /********
         * TODO_MA 马中华 https://blog.csdn.net/zhongqi2513
         *   注释： 构建两个新的 Region
         */
        final RegionInfo hri_a = RegionInfoBuilder.newBuilder(table).setStartKey(parent.getStartKey()).setEndKey(midKey).build();
        final RegionInfo hri_b = RegionInfoBuilder.newBuilder(table).setStartKey(midKey).setEndKey(parent.getEndKey()).build();

        /********
         * TODO_MA 马中华 https://blog.csdn.net/zhongqi2513
         *   注释：
         *   1、父 region 将 unassigned
         *   2、new regions will be assigned.
         */
        // Send the split request to the master. the master will do the validation on the split-key.
        // The parent region will be unassigned and the two new regions will be assigned.
        // hri_a and hri_b objects may not reflect the regions that will be created, those objects
        // are created just to pass the information to the reportRegionStateTransition().
        if(!server.reportRegionStateTransition(
                new RegionStateTransitionContext(TransitionCode.READY_TO_SPLIT, HConstants.NO_SEQNUM, -1, parent, hri_a, hri_b))) {
            LOG.error("Unable to ask master to split " + parent.getRegionNameAsString());
        }
    }

    @Override
    public void run() {
        if(this.server.isStopping() || this.server.isStopped()) {
            LOG.debug("Skipping split because server is stopping=" + this.server.isStopping() + " or stopped=" + this.server.isStopped());
            return;
        }

        /********
         * TODO_MA 马中华 https://blog.csdn.net/zhongqi2513
         *   注释：
         */
        doSplitting();
    }
}
